1. Field of the Invention
The present invention relates to a method and program for simulating the behavior of a mechanism using a computer, and in particular, to the use of both a dynamics simulation relating to the behavior of a mechanism along a time axis and using a continuous system equation including differential or algebraic equations and a kinematics simulation using a three-dimensional mechanism model containing three-dimensional shape data.
2. Description of the Related Art
Presently, when a computer is used to simulate the behavior of a continuous system such as a machine or a plant on a time axis, an object is modeled using differential equations. Then, a solution is obtained using a technique such as a numerical integration. Moreover, a technique called “hybrid modeling” may be used to express the behavior of a complicated system. A simulation using a hybrid model, which is an advanced version of a normal simulation based on simultaneous differential equations, is called a “hybrid simulation”. A system executing such a simulation behavior is sometimes called a “hybrid system”. A hybrid model intended for simulation is conceptually a combination of a continuous model expressed by simultaneous equations including ordinary differential or algebraic equations with a state transition model for expressing state transitions associated with the occurrences of events. The hybrid model enables the expression of a system in which a state expressed by a continuous system model is instantaneously switched by an external event. The hybrid model thus enables a more advanced model expression.
A language called HCC (Hybrid Concurrent Constraint Programming), created by Palo Alto Laboratory of Xerox (trade mark), U.S., is used to describe a hybrid model. The HCC is still being developed and studied in the Ames Research Center of NASA, U.S. The HCC is a kind of technique called “constraint programming”. The HCC enables ordinary differential or algebraic equations to be treated as constraints and directly described in no particular order. A hybrid model in the HCC language is completed by adding descriptions for controlling state transitions to such constraint descriptions. The HCC enables equations to be enumerated (programmed) directly as constraints to describe a complicated model.
Thus, the use of the hybrid model technique enables the characteristics of a system to be modeled using ordinary differential equations. This in turn enables a simulation as to how the behavior of the system varies over time starting with its initial state. Modeling based on differential equations enables the expression of dynamic behavior such as transitional responses or vibrations caused by disturbances. Accordingly, this modeling is also called a “dynamics simulation”.
The hybrid model technique enables the adequate modeling of an object or a phenomenon that can be expressed using differential equations. An example of application of this technique is a mechanism simulation for mechatronics equipment the mechanism of which is controlled by software. Such a mechanism simulation allows the prototyping, testing, or debugging of control software system that controls the mechanism even if there is no actual equipment for the mechanism.
On the other hand, a technique is known which uses three-dimensional shape data on the mechanism, information on connections between parts via joints to simulate geometric operations of the mechanism in a three-dimensional space. This technique corresponds to a three-dimensional CAD technique or mechanism simulation software. Reference can be made to, for example, the technique described in Jpn. Pat. Appln. KOKAI Publication No. 2001-222572. Such software cannot simulate the behavior of a system such as a vibration characteristic which operates along a time axis. However, it can handle complicated positional relationship and is sometimes called a “kinematics simulation”.
The technique described in Jpn. Pat. Appln. KOKAI Publication 2001-222572 is a well-known example in which a mechanism simulation of mechatronics equipment the mechanism of which is controlled using software is implemented within the range of a kinematics simulation and limited dynamics limitedly and already incorporated into package software.
Some pieces of mechanism simulation software incorporate the functions of a dynamics simulation to allow both kinematics and dynamics to be handled. However, such software does not correspond to a dynamics simulation that can flexibly model a complicated system in connection with the programming language shown above as the HCC. Thus, it has been impossible for a user to select an optimum modeling technique in accordance with the purpose of a simulation, create a model description on the basis of this technique, and use this model description to execute a kinematics simulation and a dynamics simulation in parallel. Moreover, if a more complicated hybrid modeling technique is used, it is difficult to allow a kinematics simulation and a dynamics simulation to cooperate with each other.